Apparatuses and methods for enhancing data rate for packet-switched (ps) data service

ABSTRACT

A wireless communication device for enhancing a data rate for a packet-switched (PS) data service is provided. The device comprises a processor configured to reference cell information corresponding to a first subscriber identity card to maintain mobility for a second subscriber identity card by using the referenced cell information when performing the PS data service with a first service network for the first subscriber identity card.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to methods and apparatuses for enhancingthe data rate for a packet-switched data service, and more particularly,for enhancing the data rate for the packet-switched data service with afirst subscriber identity card while a second subscriber identity cardis performing a scheduled measurement to maintain mobility or receivenetwork messages.

2. Description of the Related Art

With growing demand for ubiquitous computing and networking, variouswireless communication technologies have been developed, such as theGlobal System for Mobile communications (GSM) technology, General PacketRadio Service (GPRS) technology, Enhanced Data rates for GlobalEvolution (EDGE) technology, Universal Mobile Telecommunications System(UMTS) technology, Wideband Code Division Multiple Access (W-CDMA)technology, Code Division Multiple Access 2000 (CDMA 2000) technology,Time Division-Synchronous Code Division Multiple Access (TD-SCDMA)technology, Worldwide Interoperability for Microwave Access (WiMAX)technology, Long Term Evolution (LTE) technology, Long TermEvolution-Advanced (LTE-A) technology, Time-Division LTE (TD-LTE)technology, and others. Generally, a cellular phone only supports onewireless communication technology and provides a user the flexibility ofmobile communications at all times via the supported wirelesscommunication technology, regardless of his/her geographic location.Specifically in today's business world, a cellular phone is becoming anecessary business tool for conducting business conveniently. Forbusiness people, having an additional cellular phone exclusive forbusiness matters is a common choice, since they need to conduct businesswhile being out of the office or even out of the city/country. Othersmay find having an additional cellular phone as a good way tosave/control the budget for wireless service charges (including phoneservices and/or data services). However, having two or more than twocellular phones may be troublesome when one has to switch frequentlybetween the cellular phones and carry around all the cellular phoneswith himself/herself. In order to provide a convenient way of havingmultiple subscriber numbers, dual-card or multiple-card cellular phoneshave been developed, which generally have two or more wirelesscommunication modules for respectively performing wireless transmissionand reception with an individual subscriber number. The dual-card ormultiple-card design allows the wireless communication modules to beactive simultaneously and allows calls to be received on eithersubscriber numbers associated with one of the wireless communicationmodules at any time. Thus, a dual-card or multiple-card cellular phonemay be used for business and personal use with separate subscribernumbers and bills, or for travel with the second subscriber number forthe country visited.

For the dual-card or the multiple-card cellular phones with one singletransceiver, only one wireless communication module is allowed to obtainnetwork resources using the single transceiver, while another wirelesscommunication module has no control over the single transceiver.Specifically, the wireless communication module with no control over thesingle transceiver is not aware that the single transceiver is occupiedby another wireless communication module, because the two or morewireless communication modules operate independently and lack a propercommunication mechanism therebetween. For example, a dual-card cellularphone may be configured such that the single transceiver is occupied bythe first wireless communication module for performing a PS dataservice, e.g. the Multimedia Messaging Service (MMS). While thedual-card cellular phone is performing the PS data service with thefirst wireless communication module, a second wireless communicationmodule may constantly interrupt the PS data service in order to gain thecontrol of the single transceiver for performing radio measurementswhich allows the second communication module to maintain mobility orreceive network messages, such as a paging message. As a result, the PSdata rate or data throughput of the PS data service may be damaged.

Therefore, it is desirable to have a flexible way of managing theoperations between the multiple wireless communication modules formultiple subscriber identity cards, so that the operations of themultiple wireless communication modules may be coordinated to maximizeor enhance the PS data rate while maintaining the mobility for the idlesubscriber cards.

BRIEF SUMMARY OF THE INVENTION

Accordingly, embodiments of the invention provide apparatuses andmethods to enhance data rate for a PS data service. In one aspect of theinvention, a wireless communication device for enhancing a data rate fora packet-switched (PS) data service is provided. The device comprises aprocessor configured to reference cell information corresponding to afirst subscriber identity card to maintain mobility for a secondsubscriber identity card by using the referenced cell information whenperforming the PS data service with a first service network for thefirst subscriber identity card.

In another aspect of the invention, a wireless communication device forenhancing a data rate for a packet-switched (PS) data service isprovided. The device comprises a processor configured to disable aninter-RAT (Radio Access Technology) measurement for a second subscriberidentity card when performing the PS data service with a firstsubscriber identity card.

In another aspect of the invention, a wireless communication method forenhancing a data rate for a packet-switched (PS) data service isprovided. The method comprises: referencing cell informationcorresponding to a first subscriber identity card; and maintainingmobility for a second subscriber identity card by using the referencedcell information when performing the PS service with the firstsubscriber identity card.

In another aspect of the invention, a wireless communication method forenhancing a data rate for a packet-switched (PS) data service isprovided. The method comprises: disabling an inter-RAT (Radio AccessTechnology) measurement of the second subscriber identity card whenperforming the PS data service with a first subscriber identity card.

BRIEF DESCRIPTION OF DRAWINGS

The invention can be more fully understood by reading the subsequentdetailed description and examples with references made to theaccompanying drawings, wherein:

FIG. 1 is a block diagram of a wireless communications environmentaccording to an embodiment of the invention;

FIG. 2 is a diagram illustrating an exemplary LA update procedure for aGSM network;

FIG. 3 is a simplified diagram illustrating a combined GPRS/IMSI attachprocedure;

FIG. 4 is a diagram illustrating the PDP context activation procedureinitialized by an MS;

FIG. 5 is a block diagram illustrating the hardware architecture of anMS 500 according to an embodiment of the invention;

FIG. 6 shows a block diagram illustrating the hardware architecture ofan MS 600 according to another embodiment of the invention;

FIG. 7 is a block diagram illustrating the hardware architecture of anMS 700 coupled with three subscriber identity cards and a single antennaaccording to an embodiment of the invention;

FIG. 8 is a block diagram illustrating the software architecture of anMS according to an embodiment of the invention;

FIG. 9 is a diagram illustrating channel occupancy time for an MS thatmonitors a 2G CS paging channel and makes 2G power measurements in a 3Gpacket transfer mode according to an embodiment of the invention;

FIG. 10 is a flow chart illustrating a method for enhancing the datarate for a packet-switched (PS) data service associated with the secondsubscriber identity card when the protocol stack handler 910 is in theidle mode for the first subscriber identity card by using the softwarearchitecture of FIG. 8 according to an embodiment of the invention;

FIG. 11 is a message sequence chart illustrating the method forenhancing the data rate for a packet-switched (PS) data serviceassociated with the first subscriber identity card when the secondsubscriber identity card is performing a scheduled measurement accordingto the embodiment of FIG. 10;

FIG. 12A and FIG. 12B is a flow chart illustrating a method forenhancing the data rate for a packet-switched (PS) data serviceassociated with the second subscriber identity card when protocol stackhandler 910 is in the idle mode for the first subscriber identity cardby using the software architecture of FIG. 8 according to anotherembodiment of the invention;

FIG. 13 is a message sequence chart illustrating the method forenhancing the data rate for a packet-switched (PS) data serviceassociated with the second subscriber identity card when the protocolstack handler 910 is in the idle mode for the first subscriber identitycard according to the embodiment of FIG. 12A and FIG. 12B;

FIG. 14 is a block diagram illustrating the software architecture of anMS according to another embodiment of the invention;

FIG. 15A and FIG. 15B is a flow chart illustrating a method forenhancing the data rate for a packet-switched (PS) data serviceassociated with the second subscriber identity card when the protocolstack handler 910 is in the idle mode by using the software architectureof FIG. 14 according to an embodiment of the invention; and

FIG. 16A and FIG. 16B is a flow chart illustrating a method forenhancing the data rate for a packet-switched (PS) data serviceassociated with the second subscriber identity card when the protocolstack handler 910 is in the idle mode for the first subscriber identitycard by using the software architecture of FIG. 14 according to anotherembodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. It should be understood that the embodimentsmay be realized in software, hardware, firmware, or any combinationthereof.

FIG. 1 is a block diagram of a wireless communications environmentaccording to an embodiment of the invention. The wireless communicationsenvironment 100 comprises a mobile station (MS) 110, and servicenetworks 120, 130, 140 and 150. The MS 110 may wirelessly communicatewith the service networks 120, 130, 140 and 150 with one to fourseparate subscriber numbers and/or four separate subscriber identities,after camping on one to four cells. The cell may be managed by a node-B,a base station (BS), an advanced BS (ABS), an enhanced BS (EBS) orothers. However, the communication is only allowed to be performed withone of the four service networks 120, 130, 140 and 150 at a given time.The service networks 120, 130, 140 and 150 may be in compliance with anyof the GSM/GPRS/EDGE, WCDMA, CDMA 2000, UMTS, TD-SCDMA, WiMAX, LTE,LTE-A, and TD-LTE technologies. The service networks 120, 130, 140 and150 may be operated by different or the same operator using the same ordifferent Radio Access Technologies (RATs). For example: the servicenetwork 120 and 130 may be operated by different operators of the corenetwork operator A and core network operator B, while both the servicenetworks 140 and 150 may be operated by the same core network operatorC. The MS 110 may be equipped with two single RAT subscriber identitycards and one dual RAT subscriber identity card or alternatively, the MS110 may be equipped with two dual RAT subscriber identity cards or foursingle RAT subscriber identity cards, wherein the invention is notlimited thereto. The single RAT subscriber identity cards may be used tocommunicate wirelessly with one service network respectively, such asthe service network 120 or 130, while the dual RAT subscriber identitycard may be used to communicate wirelessly with the more than oneservice network, such as the service network 140 and 150 The dual RATsubscriber identity card may be configured to communicate with theservice networks 140 and 150 at the same time or only communicate withone of the service networks 140 and 150 at a time, depending on the typeof implementation. The subscriber numbers may be provided by threeseparate subscriber identity cards in compliance with the specificationsof the technologies employed by the service networks 120, 130, 140 and150. For example, the service network 120 may be a GSM/GPRS/EDGE system,and correspondingly, one of the single RAT subscriber identity cards maybe a Subscriber Identity Module (SIM) card, while the service network130 may be a TD-SCDMA system and correspondingly, the other one of thesingle RAT subscriber identity cards may be a CDMA subscriber IdentityModule (CSIM) card. The service network 140 may be a GSM/GPRS/EDGEsystem while the service network 150 may be a UMTS system andcorrespondingly, the dual RAT subscriber identity cards may be aUniversal SIM (USIM) card that supports the GSM/GPRS/EDGE RAT and theUMTS RAT. The three subscriber identity cards equipped by the MS 110 maybe taken as an example. The MS 110 may also be equipped with 2, 3, ormore subscriber identity cards and be adapted to 2, 3, or more wirelesstelecommunication technologies according to different designrequirements of the MS 110.

The MS 110 wirelessly accesses the Internet resources, such as e-mailtransmissions, Web browsing, file upload/download, instant messaging,streaming video, voice over IP (VoIP) or others, or makes a wirelessphone call. In addition, a computer host or a notebook may beconnected/coupled to the MS 110 and wirelessly access Internet resourcestherethrough. The MS 110 may be operated in an idle mode or dedicatedmode in GSM systems for the inserted SIM card. In an idle mode, the MSsearches for or measures a Broadcast Control Channel (BCCH) with abetter signal quality from a cell provided by a specific servicenetwork, or is synchronized to the BCCH of a specific cell, wherein itis continuously ready to perform a random access procedure on a RandomAccess Channel (RACH) for requesting for a dedicated channel. In thededicated mode, the MS 110 occupies a physical channel and tries tosynchronize therewith, and establishes logical channels and performsswitching therethrough. As the MS 110 is equipped with one or moresubscriber identity cards, the MS 110 may be operated in an idle modeand connected mode, for a WCDMA or TD-SCDMA network, for each insertedUSIM card.

The MS may perform power measurements to candidate cells and use themeasured signal quality and/or signal strength as an input for handoverand cell reselection decisions. In the case where the MS is in the idlemode, the list of the neighboring GSM cell Broadcast Control Channel(BCCH) frequencies may be transmitted with its own BCCH frequency andthe MS may listen for the BCCH frequencies and perform a powermeasurement for the GSM Received Signal Strength Indication (RSSI) ofthe BCCH, which is a wideband received power within the GSM channelbandwidth. In the case of a UMTS or WCDMA network, although the samewideband frequency is used by adjacent cells, the cells are physicallyidentified by their different scrambling codes, and the MS mayconstantly monitor the Common Pilot Channel (CPICH) for power levels(e.g. Energy over Noise Ratio (Ec/No), Received Signal Code Power(RSCP), and so on). The information may then be used to assess whetherthe UMTS/WCDMA cell should be added to the ranking candidates for cellreselection. The MS may make a cell reselection decision depending ondifferent cell reselection criteria corresponding to each radio accesstechnology (RAT). For example, for a GSM network, the cell reselectioncriteria may be based on the C1 and C2 criterions. Alternatively, for aUMTS network or a WCDMA network, there may be other cell reselectioncriteria such as an R-criterion. The MS may check for the Location AreaIdentity (LAI) from the system information message present on the BCCH,the broadcast channel (BCH), or others, after a cell reselection isperformed, wherein the LAI represents a unique identity for differentLocation Area (LA). When the new cell and the old cell belong todifferent LAs, an LA update may be required.

LA update is a procedure that makes the network aware of the MSlocation. This is a prerequisite for mobility where the MS movement canbe tracked and its position known in the case of incoming MT calls, MTshort message services (MT SMS) or others. Generally, the wirelessnetwork architecture for any of the GSM/GPRS/EDGE, WCDMA, CDMA 2000,WiMAX, TD-SCDMA, LTE, LTE-A, TD-LTE, or other technologies embraces thechallenge of supporting such functions as paging, location updating andconnection handover/reselection. The handover/reselection mechanismguarantees that whenever the mobile is moving from one base stationarea/cell to another, the radio connection is handed over or reselectedto the target base station without interruption. The location updateprocedure, alternatively, enables the network of the supported RAT tokeep track of the subscriber camping within the coverage of the network,while a paging message is used to reach the MS to which a call isdestined (e.g. MT call, MT SMS or others). Each LA is uniquelyidentified with a Location Area Identity (LAI) and the LAI consists of aMobile Country Code (MCC)+Mobile Network Code (MNC)+LA code (LAC).

FIG. 2 is a diagram illustrating an exemplary LA update procedure for aGSM network. In a GSM LA update procedure, the MS may firstly requestfor a channel by sending a Channel Request (CHAN_REQ) message on theRACH, the BSS may respond by sending an Immediate Assignment Commandmessage (IMMASS_CMD) on the AGCH. Then, the MS may switch to theassigned SDCCH and reply to the BSS with a Location Update Request(LOC_UPD_REQ). Included in the LOC_UPD_REQ is the TMSI that the MS iscurrently using as well as the Location Area Identifier (LAI) of theVisitor Location Register (VLR) it is leaving, and the BTS mayacknowledge receipt of the message (not shown) to the BSS. Anauthentication procedure is then carried out. In the case where theauthentication is unsuccessful, the procedure is aborted. In the casewhere the authentication is successful, the ciphering procedure isperformed.

Before the network provides any services to the MS, the network requiresthe MS to authenticate itself. During the authentication and cipheringprocess, the BSS sends an Authentication Request (AUTH_REQ) messageincluding a random number (RAND) to the MS, the RAND is a 128-bit randomchallenge generated by the Home Location Register (HLR) forauthentication. The MS calculates a proper signed response (SRES) basedon the RAND that was given and sends the SRES to the BSS in anAuthentication Response (AUTH_RESP) message. The BSS verifies the SRES.If the SRES is correct then the MS is authenticated and allowed toaccess the network. Once the MSCNLR has authenticated the MS, theMSC/VLR may order the BSS and MS to switch to a cipher mode using theCIPH_MOD_CMD message. Once the MS in cipher mode, the VLR will normallyassign a new TMSI to the MS. Once the MS is authenticated and in thecipher mode, the MSC/VLR may send a Location Update Accept message(LOC_UPD_ACC) through the BSS to the MS. The LOC_UPD_ACC may have a TMSIassignment in it. The MS may then respond to the BSS with a TMSIReallocation Complete message (TMSI_REAL_COM) indicating that it hasreceived the TMSI. The BSS then sends the MS a Channel Release message(CHAN_REL) instructing it to go into idle mode. The BSS then un-assignsthe SDCCH. As far as the MS is concerned, the location update has beencompleted. The LA update procedure in WCDMA, TD-SCDMA or UMTS systems issimilar to that of the GSM systems and is omitted herein.

For the GPRS systems, networks based on the Internet Protocol (IP) (e.g.the global Internet or private/corporate intranets) and X.25 networksare supported. Before one of the (U)SIM cards of an MS can use the GPRSservice, the MS needs to perform a GPRS attach procedure to attach tothe GPRS network with one (U)SIM card. The GPRS attach procedure is aprocess during which the mobile device informs the network about itspresence in the network. In a GPRS attach procedure, the SGSNestablishes a mobility management (MM) context relating to the mobilityand security for the MS. FIG. 3 is a simplified diagram illustrating acombined GPRS/IMSI attach procedure. In the combined GPRS/IMSI attachprocedure, the MS first sends an Attach Request message to a ServingGPRS Support Node (SGSN), wherein the message sent to the new ServingGPRS Support Node (SGSN) contains the last assigned Packet TemporaryMobile Subscriber Id (P-TMSI) or IMSI, and the location areainformation, etc. The new SGSN then queries the old SGSN (the previousattached SGSN) for the identity of the MS by exchanging Identity Requestand Identity Response messages. Then, the new SGSN requests moreinformation from the MS to authenticate itself by exchanging IdentityRequest and Identity Response messages. After the MS identity ischecked, an authentication similar to the one described in FIG. 2 isperformed, wherein the authentication is mandatory if no mobilitymanagement (MM) context for the MS exists anywhere in the servicenetwork. After authentication, an optional International MobileEquipment Identity number (IMEI) check may be performed to check the MSequipment. Then, core network signaling takes place, wherein any activePDP context in the new SGSN for the MS is deleted, and signalingexchange takes place between the new SGSN and the Home Location Register(HLR)/Visitor Location Register (VLR) to update the location of the MS.The SGSN selects a Radio Priority SMS, and sends an Attach Accept (whichmay include P-TMSI, VLR TMSI, P TMSI Signature, Radio Priority SMS, IMSvoice over PS Session Supported Indication, or Emergency Service Supportindicator) message to the MS. Then, if the P-TMSI or VLR TMSI has beenchanged, the MS acknowledges the received TMSI(s) by returning an AttachComplete message to the SGSN, and the SGSN confirms the VLR TMSIre-allocation by sending a TMSI Reallocation Complete message to theVLR.

To exchange data packets with external Public Data Networks (PDNs) aftera successful GPRS attach procedure, the MS applies for an address usedin the PDN, wherein the address is called a Packet Data Protocol (PDP)address. In the case where the PDN is an IP network, the PDP address isan IP address. For each session, a so-called PDP context is created,which describes the characteristics of the session. The PDP contextdescribes PDP types (e.g. IPv4, IPv6 or others), wherein the PDP addressis assigned to the MS, and the requested Quality of Service (QoS) classand the address of a Gateway GPRS Support Node (GGSN) that serves as theaccess point to the external network. FIG. 4 is a diagram illustratingthe PDP context activation procedure initialized by an MS. With theACTIVATE PDP CONTEXT REQUEST message, the MS informs the SGSN of therequested PDP context. After that, the typical GSM security functions(e.g. authentication of the MS) are performed. If the access is granted,the SGSN will send a CREATE PDP CONTEXT REQUEST message to the affectedGGSN. The GGSN creates a new entry in its PDP context table, whichenables the GGSN to route data packets between the SGSN and the externalPDN. Next, the GGSN confirms the request to the SGSN with a CREATE PDPCONTEXT RESPONSE message. Finally, the SGSN updates its PDP contexttable and confirms the activation of the new PDP context to the MS withan ACTIVATE PDP CONTEXT ACCEPT message. Note that for an MS using bothCS and PS services, it is possible to perform a combined GPRS/IMSIattach procedure (as illustrated in FIG. 3). The disconnection from theGPRS network is called GPRS detachment, which may be initiated by the MSor by the GPRS network.

In addition, IP packets are transmitted by being encapsulated within theGPRS backbone network. The IP packet transmission is achieved using theGPRS Tunneling Protocol (GTP). That is, GTP packets carry the user's IPpackets. The GTP is defined both between GPRS Supports Nodes (GSNs)within the same Public Land Mobile Network (PLMN) and between GSNs ofdifferent PLMNs. The GTP contains procedures in the transmission planeas well as in the signaling plane. In the transmission plane, the GTPemploys a tunnel mechanism to transfer user data packets. In thesignaling plane, the GTP specifies a tunnel control and managementprotocol. The signaling is used to create, modify, and delete tunnels. ATunnel Identifier (TID), which is composed of the IMSI of the (U)SIMcard and a Network Layer Service Access Point Identifier (NSAPI)uniquely indicates a PDP context. Below the GTP, a transmission controlprotocol (TCP) is employed to transport the GTP packets within thebackbone network. In the network layer, IP is employed to route thepackets through the backbone. Taking the GSM systems for example, afterthe MS successfully attaches to a GPRS network with a (U)SIM card, acell supporting GPRS may allocate physical channels for the GPRStraffic. In other words, the radio resources of a cell are shared by theMS with the (U)SIM card.

An MS carries out the process of a Public Land Mobile Network (PLMN)search procedure each time the MS is switched on or when the MS isrecovering from a state of lack of coverage (e.g. a limited servicestate). The PLMN search procedure is the process of selecting the bestPLMN available. If it is in the home PLMN service area, the MS isprogrammed to select the home PLMN, wherein the home PLMN is a PLMNwhere the Mobile Country Code (MCC) and the Mobile Network Code (MNC) ofthe PLMN identity match the MCC and MNC of any entry in EHPLMN file ofthe USIM card or the International Mobile Subscriber Identity (IMSI) ofthe SIM card if EHPLMN does not exist inside of the MS. If the home PLMNis not found, another PLMN from a priority list is selected and a cellbelonging to that PLMN is searched.

The MS looks for a suitable cell of the chosen PLMN and chooses thatcell to provide available services, and tunes to its control channel.This choosing is known as a “cell selection” or “camping on the cell”.The MS will then register its presence in the registration area of thechosen cell if necessary, by means of a location registration (LR), GPRSattach or IMSI attach procedure (as described in FIG. 3). Initial cellselection is the process of the MS finding the best possible cell on anewly selected PLMN in order to receive the system information on theBCCH from the selected PLMN, initiate/receive a call, or receive cellbroadcast messages. Two methods of searching for a suitable cell arepossible, namely the normal cell selection method and the stored listcell selection method. In the normal cell selection method, the MS looksfor a cell which satisfies 5 constraints for a suitable cell by checkingcells in a descending order of received signal strength. Specifically,the 5 constraints are listed as follows:

-   -   The suitable cell should be a cell of the selected PLMN or, if        the selected PLMN is equal to the last registered PLMN, an        equivalent PLMN.    -   The suitable cell should not be “barred”.    -   The suitable cell should not be in an LA which is in the list of        “forbidden LAs for roaming”    -   The radio path loss between MS and base station must be below a        threshold set by the PLMN operator.    -   The suitable cell should not be a Support of Localised Service        Area (SoLSA) exclusive cell for which the MS is not subscribed        to.

If the MS is unable to find a suitable cell to camp on, or the (U)SIM isnot inserted, or if it receives certain responses to an LR request(e.g., “illegal MS”), the MS may attempt to camp on a cell irrespectiveof the PLMN identity, and enter a “limited service” state in which itcan only attempt to make emergency calls. In the case when the MS entersthe limited service state due to “No suitable cell”. If the MS is unableto obtain normal services from a home PLMN, the MS attempts to camp onan acceptable cell, irrespective of its PLMN identity, so that emergencycalls can be made if necessary. Specifically, an “acceptable cell” is acell on which the UE may camp to obtain limited services (originateemergency calls and receive ETWS if supported). Such a cell shall not bebarred and shall fulfill the cell selection criteria. The MS may performa PLMN search procedure periodically to recover from the limited servicestate. During the PLMN search procedure, the MS may perform a power scanto find out proper cells to camp on. For the GSM technology, during thepower scan, the processor in the GSM/GPRS Baseband chip may instruct theGSM/GPRS RF module to perform signal level measurements on frequenciesof the current network. After finding potential candidates based on thereceived signal level RXLREV (that is, completion of the power scan),each carrier is investigated by the processor in the GSM/GPRS Basebandchip for the presence of a frequency correction channel (FCCH),beginning with the strongest signal. A FCCH burst (FCB) is an all-zerosequence that produces a fixed tone enabling the GSM/GPRS RF module tolock its local oscillator to the base station clock. Its presenceidentifies the carrier as a BCCH carrier for synchronization. The MSthen uses a synchronization burst (SB) of the synchronization channel(SCH) following the FCCH burst and has a long training sequence to finetune the frequency correction and time synchronization. The processor inthe GSM/GPRS Baseband chip obtains and stores the exact channelconfiguration of the selected cell from the BCCH data as well as thefrequencies of the neighboring cells. After completely collecting andstoring information regarding the exact channel configuration andneighboring cells in a memory or a storage device, the GSM/GPRS moduleperforms a location update procedure through a traffic channel (TCH) toinform the cellular network of its location. After the PLMN searchprocedure is completed, the MS may perform normal circuit switched (CS)or PS operations with the service network it is subscribed to.

FIG. 5 is a block diagram illustrating the hardware architecture of anMS 500 according to an embodiment of the invention. The MS 500 isequipped with a baseband chip 610, and a single RF module 620 coupledwith an antenna 630. The baseband chip 610 may contain multiple hardwaredevices to perform baseband signal processing, including analog todigital conversion (ADC)/digital to analog conversion (DAC), gainadjusting, modulation/demodulation, encoding/decoding, and so on. Inparticular, the baseband chip 610 may comprise a processor 612. In anembodiment, the processor 612 may be configured to execute instructionsstored in a memory device of the MS 600 or other removable memorydevices accessible to the processor 612. By executing storedinstructions or operating in accordance with hard coded instructions,the processor 612 may control the operation of the MS 500 by directingfunctionality of the MS 600 associated with enhancing the data rate fora PS data service associated with one of the subscriber identity cardswhen another subscriber identity card is performing a scheduledmeasurement to maintain mobility or to receive messages. The processor612 may also be configured to coordinate operations between differentmodules of the MS 500, such as the MMI 650, the RF module 620, and thesubscriber identity cards 10, 20 and 30. The RF module 620 may receiveRF wireless signals from the antenna 630, convert the received RFwireless signals to baseband signals, which are then processed by thebaseband chip 610, or receive baseband signals from the baseband chip610 and convert the received baseband signals to RF wireless signals,which are later transmitted via the antenna 630. The RF module 620 mayalso contain multiple hardware devices to perform radio frequencyconversions. For example, the RF module 620 may comprise a mixer tomultiply the baseband signals with a carrier oscillated in the radiofrequency of the wireless communications system, wherein the radiofrequency may be 900 MHz, 1800 MHz or 1900 MHz utilized in GSM systems,or may be 900 MHz, 1900 MHz or 2100 MHz utilized in the UMTS and WCDMAsystems, or others depending on the radio access technology (RAT) inuse. As shown in FIG. 5, the subscriber identity cards 10, 20 and 30 areplugged into three sockets of the MS 500. The MS 500 may furthercomprise a multiple-card controller 640 coupled or connected between thebaseband chip 610 and the subscriber identity cards 10, 20 and 30. Themultiple-card controller 640 powers the subscriber identity cards 10, 20and 30 with the same or different voltage levels according torequirements thereof by a power management integrated chip (PMIC) and abattery, wherein the voltage level for each subscriber identity card isdetermined during initiation. The baseband chip 610 reads data from oneof the subscriber identity cards 10, 20 and 30, and writes data to oneof the subscriber identity cards 10, 20 and 30 via the multiple-cardcontroller 640. In addition, the multiple-card controller 640selectively transfers clocks (CLK), resets (RST), and/or input/outputdata signals (I/O) to the subscriber identity cards 10, 20 and 30according to instructions issued by the processor 612. The baseband chip610 may support one or more of the GSM/GPRS/EDGE, UMTS, WCDMA, CDMA2000, WiMAX, TD-SCDMA, LTE, and TD-LTE technologies. The subscriberidentity cards 10, and 30 may be any of the Subscriber Identity Module(SIM) cards, Universal SIM (USIM) cards, Removable User Identity Module(R-UIM), and CDMA Subscriber Identity Module (CSIM) cards, whichcorrespond to the wireless communications technologies supported by thebaseband chip 610. Each subscriber identity cards 10, 20 and 30 in theMS 500 may support at least one RAT. For example, the subscriberidentity card 10 may be a SIM card, which supports the 2G RAT, such asthe GSM/GPRS/EDGE technologies. The subscriber identity card 20 may be aUSIM card, which contains the application to support the 2G/3G RATs,such as the GSM/GPRS/EDGE technologies and the UMTS technology. Thesubscriber identity card 30 may be a CSIM card, which contains theapplication to support the 2G/3G RATs, such as the GSM/GPRS/EDGEtechnologies and the CDMA technology. The MMI 650 may include akeyboard, a touch panel, a touch screen, a display device, a joystick, amouse and/or a scanner, removable memory devices, and so on. The MS 500may therefore simultaneously camp on as many cells provided by eitherthe same network operator or different network operators for the pluggedsubscriber identity cards 10, and 30, and operate in different modessuch as a connected mode, idle mode, cell Dedicated Channel (CELL_DCH)mode, cell Forward access channel (CELL_FACH) mode, cell Paging Channel(CELL_PCH) mode and UTRAN Registration Area Paging Channel (URA_PCH)mode using the single RF module 620, the baseband chip 610, and theprocessor 612.

Alternatively, FIG. 6 shows a block diagram illustrating the hardwarearchitecture of an MS 600 according to another embodiment of theinvention. Similar to FIG. 5, the baseband chip 710 performs basebandsignaling processing, such as analog to ADC/DAC, gain adjusting,modulation/demodulation, encoding/decoding, and so on. The baseband chip710 may also comprise a processor 612, which controls the operation ofthe MS 600 by directing functionality of the MS 600 associated withenhancing the data rate for a PS data service associated with one of thesubscriber identity cards when another subscriber identity card isperforming a scheduled measurement to maintain mobility or to receivemessages. And similarly, the MMI 650 may also include variousinput/output modules. However, the connections from the MS 600 to thesubscriber identity cards 10, 20 and 30 are independently handled bythree interfaces (I/F) provided from the baseband chip 710, wherein eachsubscriber identity cards 10, 20 and 30 in the MS 500 may support atleast one RAT. It is to be understood that the hardware architecture asshown in FIG. 5 or 6 may be modified to include less than three or morethan three subscriber identity cards, and the invention is not limitedthereto.

FIG. 7 is a block diagram illustrating the hardware architecture of anMS 700 coupled with three subscriber identity cards and a single antennaaccording to an embodiment of the invention. The exemplary hardwarearchitecture may be applied to any MS utilizing GSM/GPRS/EDGE, WCDMA,CDMA 2000, UMTS, TD-SCDMA, WiFi, WiMAX, LTE, LTE-A, or TD-LTEtechnologies. In the exemplary hardware architecture, three Radio AccessTechnology (RAT) modules, the GSM/GPRS module 720, the WCDMA module 730and the UMTS module 740 may share a single antenna 750, and each RATmodule contains at least an RF module and a baseband chip, to camp on acell and operate in a stand-by mode, idle mode, connected mode, CELL_DCHmode, CELL_FACH mode, CELL_PCH mode, URA_PCH mode, and so on. As shownin FIG. 7, the GSM/GPRS baseband chip 721 is coupled to a GSM/GPRS RFmodule 722, the WCDMA baseband chip 731 is coupled to a WCDMA RF moduleA 732, and the UMTS baseband chip 741 is coupled to a UMTS RF module742. Each baseband chip includes a processor, e.g. the GSM/GPRS basebandchip 721 includes a processor A 723, the WCDMA baseband chip 731includes a processor C 733, and the UMTS baseband chip 741 includes aprocessor D 743. In addition, when operating in a specific mode, eachRAT module may interact with one or more specific subscriber identitycard as required, such as the (U)SIMs 772, 774 or 776. A multiplexer 770is connected between the (U)SIM 772, 774 or 776 and the baseband chips721/731/741 to enable bi-directional communications between the (U)SIM772, 774 or 776 with the relevant baseband chips 721, 731, or 741. Forexample, the multiplexer 770 may be configured to enable thebi-directional communication between the (U)SIM 774 and the GSM/GPRSbaseband chip 721 or the UMTS baseband chip 741. A switching device 760is coupled between the shared antenna 750 and multiple Low NoiseAmplifiers (LNAs). The switching device 760 may connect the antenna 750to one LNA to allow the RF signals to pass through the connected LNA.Each LNA amplifies signals in a 2G/3G/4G band received by the sharedantenna 750 and provides the signals to corresponding RF modules722/732/742, wherein the 2G/3G/4G band may be a 900 MHz, 1800 MHz, 1900MHz, or 2100 MHz band, or others. Once one of the baseband chips721/731/741 attempts to perform a transceiving activity, such as atransmission (TX) or a reception (RX) activity, it issues a controlsignal Ctrl_GSM_band_sel, Ctrl_UMTS_band_sel or Ctrl_WCDMA_band_sel todirect the switching device 760 to connect the shared antenna 750 to adesignated LNA. By issuing the control signals of Ctrl_GSM_band_sel,Ctrl_UMTS_band_sel or Ctrl_WCDMA_band_sel, each processor 723/733/743may also control the operation associated with enhancing the data ratefor a PS data service associated with one of the subscriber identitycards when another subscriber identity card is performing a scheduledmeasurement to maintain mobility or to receive messages. It is to beunderstood that the GSM/GPRS module 720, the WCDMA module B 730 and theUMTS module B 740 are given as examples. For those skilled in the art,any of the GSM/GPRS/EDGE, WCDMA, CDMA 2000, WiMAX, TD-SCDMA, LTE, LTE-A,TD-LTE, or other technologies may be used to implement the RAT modules720, 730 and 740 in the hardware architecture without departing from thespirit of the invention, and the invention is not limited thereto. It isto be understood that the hardware architecture as shown in FIG. 7 maybe modified to include less or more subscriber identity cards and/or RFmodules relating to different RATs, and the invention is not limitedthereto.

A SIM card typically contains user account information, an internationalmobile subscriber identity (IMSI), and a set of SIM application toolkit(SAT) commands. In addition, storage space for phone book contacts isprovided in SIM cards. A micro-processing unit (MCU) of a baseband chip(referred to as a Baseband MCU hereinafter) may interact with the MCU ofa SIM card (referred to as a SIM MCU hereinafter) to fetch data or SATcommands from the plugged SIM card. An MS is immediately programmedafter the SIM card is plugged in. SIM cards may also be programmed todisplay custom menus for personalized services. A SIM card may furtherstore a Home Public-Land-Mobile-Network (HPLMN) code to indicate anassociated network operator, wherein the HPLMN code contains a MobileCountry Code (MCC) followed by a Mobile Network code. To furtherclarify, an IMSI is a unique number associated with a global system formobile communication (GSM) or a universal mobile telecommunicationssystem (UMTS) network user. An IMSI may be sent by an MS to a GSM orUMTS network to acquire other detailed information of the network userin the Home Location Register (HLR) or to acquire the locally copieddetailed information of the network user in the Visitor LocationRegister (VLR). Typically, an IMSI is 15 digits long or shorter (forexample, the MTN South Africa's IMSIs are 14 digits long). The first 3digits are the Mobile Country Code (MCC), and are followed by the MobileNetwork Code (MNC), either 2 digits (European standard) or 3 digits(North American standard). The remaining digits are the mobilesubscriber identification numbers (MSIN) for a GSM or UMTS network user.

A USIM card is inserted in an MS for UMTS (also called 3G) telephonycommunication. A USIM card stores user account information, IMSIinformation, authentication information and a set of USIM ApplicationToolkit (USAT) commands therein, and provides storage space for textmessages and phone book contacts. A USIM card may further store a HomePublic-Land-Mobile-Network (HPLMN) code therein to indicate anassociated network operator. A Baseband MCU may interact with an MCU ofa USIM card (referred to as a USIM MCU hereinafter) to fetch data orUSAT commands from the plugged in USIM card. Note that the phone book onthe USIM card has been greatly enhanced from that of the SIM card. Forauthentication purposes, the USIM card may store a long-term presharedsecret key K, which is shared with the Authentication Center (AuC) inthe network. The USIM MCU may verify a sequence number that must bewithin a range using a window mechanism to avoid replay attacks, and isin charge of generating the session keys CK and IK to be used in theconfidentiality and integrity algorithms of the KASUMI (also termedA5/3) block cipher in UMTS. An MS is immediately programmed afterplugging in the USIM card. In addition, an R-UIM or CSIM card isdeveloped for a CDMA MS that is equivalent to the GSM SIM and 3G USIM,except that it is capable of working in CDMA networks. The R-UIM or CSIMcard is physically compatible with the GSM SIM card, and provides asimilar security mechanism for CDMA networks and network users.

FIG. 8 is a block diagram illustrating the software architecture of anMS according to an embodiment of the invention. The exemplary softwarearchitecture may contain the protocol stack handlers 910 and 920, and anapplication layer 930. The protocol stack handlers 910 is configured toexecute operations related to the first subscriber identity card whilethe protocol stack handlers 920 is configured to execute operationsrelated to the second subscriber identity card. In one embodiment, thefirst subscriber identity card may support one or more RATs (e.g. a SIMcard that supports a single GSM/GPRS RAT or a CSIM card that supportsboth the CDMA RAT and the GSM/GPRS RAT), wherein the second subscriberidentity card may also support one of the RATs that is supported by thefirst subscriber identity card (e.g. the CDMA RAT or the GSM/GPRS RAT).The protocol stack handler 910 may be configured to communicate with afirst service network and/or a second service network (e.g. the servicenetwork 130 and/or 150) with a first subscriber identity card (e.g. thesubscriber identity card 30), while the protocol stack handler 920 isconfigured to communicate with a third service network (e.g. the servicenetwork 140) with a second subscriber identity card (e.g. the subscriberidentity card 20), wherein the third service network may be configuredwith the same or different RAT as the first and/or the second servicenetwork. The application layer 930 may contain program logics forproviding the MMI 650 as illustrated in FIG. 5 and FIG. 6. The MMI isthe means by which people interact with the MS, and the MMI may containscreen menus and icons, a keyboard, shortcuts, command language, andonline help, as well as physical input devices, such as buttons, a touchscreen, and a keypad. By the input devices of the MMI, users maymanually touch, press, click, or move the input devices to operate theMS for making or answering a phone call, texting, or sending or viewingshort messages, multimedia messages, e-mails or instant messages,surfing the Internet, or others. Correspondingly, the application layer930 may contain a web browser allowing a user to browse the Internet, astreaming video player allowing a user to watch streaming videos online,an e-mail client allowing a user to edit, browse, or send e-mailmessages, and/or a data call agent allowing a user to initiate orreceive a data call.

When the protocol stack handler 920 is performing a packet-switched (PS)data service on-line, the protocol stack handler 910, when executed by aprocessor (e.g. 612 of FIG. 5 or 6, or 723, 733 or 743 of FIG. 7), maydirect requisite circuits of a Baseband chip (e.g. 610 of FIG. 5, 710 ofFIG. 6, or 721, 731 or 741 of FIG. 7) with a relevant RF module (e.g.620 of FIG. 5 or 6, or 722, 732 or 742 of FIG. 7) to constantly listento the paging channel for paging messages sent from the first servicenetwork and/or the second service network. In an embodiment, theprotocol stack handler 910 may listen to the paging channel (PCH) forpaging messages within an associated Discontinuous Reception (DRX) groupor an associated paging group signaled by a higher layer when theassociated first or second service network is a GSM network. In anotherembodiment, when the associated first or second service network is aWCDMA or UMTS network, the protocol stack handler 910 may listen to theassociated paging indicator (PI) messages which are transmitted in thePaging Indicator Channel (PICH) in the paging occasion at each DRXcycle, and listen to the PCH in an associated Secondary Common ControlPhysical Channel (S-CCPCH) for paging messages when the PICH carries aPI message intended for the MS. Specifically, the protocol stack handler910 may listen to the PI on the PICH or the paging messages on the PCHby taking control of the single radio hardware resource, which causes aninterruption of the PS data service associated with the protocol stackhandler 920 and damages the data rate. When the protocol stack handler910 receives a paging message intended for the MS for a CS service suchas an MT call, an MT SMS, or others, the protocol stack handler 910 mayrequest the protocol stack handler 920 to suspend the PS data service.

In another embodiment, the protocol stack handler 910, when executed bythe processor, may direct requisite circuits of the Baseband chip withthe relevant RF module—to perform power measurements with the firstservice network or the second service network while the protocol stackhandler 920 performs a PS data service. From the power measurementresults, the protocol stack handler 910 may make cell reselectiondecisions depending on different cell reselection criteria correspondingto each radio access technology (RAT).

FIG. 9 is a diagram illustrating channel occupancy time for an MS thatmonitors a 2G CS paging channel and makes 2G power measurements in a 3Gpacket transfer mode according to an embodiment of the invention. Assumethat the protocol stack handler 920, when executed by the processor,performs a packet-switched (PS) data service (e.g. e-mail, web browsingand so on) on-line with a second service network (e.g. a UMTS servicenetwork 150) with a second subscriber identity card (e.g. the subscriberidentity card 40), and the protocol stack handler 910, when executed bythe same or a different processor, communicates with a first servicenetwork (e.g. the 2G GSM/GPRS/EDGE service network 130) with a firstsubscriber identity card (e.g. the subscriber identity card 20). Theprotocol stack handler 910 may constantly listen to the 2G pagingchannel in a common control channel (CCCH) for paging messages sent fromthe first service network (e.g. the CS paging 902). The protocol stackhandler 910 may synchronize itself with the paging cycle associated withthe first service network, calculate paging occasions of the pagingchannel, and wake up at the right moment in time to listen to the CSpaging 902 (e.g. by taking control of the single radio resource hardwaresuch as a single antenna or single RF module over the protocol stackhandler 920). If no paging messages intended for the MS are received,the protocol stack handler 910 returns the control of the radio resourcehardware back to the protocol stack handler 920, and the protocol stackhandler 920 may continue with the CS paging 902. While the protocolstack handler 910 listens to the CS paging 902, the 3G PS data transfer906 performed by the protocol stack handler 920 may experience amomentary discontinuous data reception, and the protocol stack handler920 may recover the lost data packets by requesting for retransmissionor by other data recovery methods. It is assumed that those skilled inthe art are knowledgeable about data retransmission techniques, andthus, detailed examples are not provided further. As described above,since the monitoring of the CS paging 902 may constantly interrupt the3G PS data transfer 906, the data rate associated with the secondidentity card may be damaged due to the monitoring of the 2G CS pagingchannel made for the first subscriber identity card. Similarly, 3G CSpaging channel monitoring is also performed according to the associatedDRX cycle. The associated paging indicators (PI) which are transmittedin the Paging Indicator Channel (PICH) in the paging occasion at eachDRX cycle is monitored, and the associated S-CCPCH for paging messagesis monitored if the PICH carries a PI message intended for the MS (e.g.by taking control of the single radio resource hardware such as a singleantenna or single RF module over the protocol stack handler 920). ThePICH is a fixed rate (SF=256) physical channel used to carry the PI,wherein the PICH is always associated with an S-CCPCH to which a pagingchannel (PCH) transport channel is mapped, and a PI set in a PICH framemeans that the paging message is transmitted on the PCH in the S-CCPCHframe starting t_(PICH) chips (t_(PICH)=7680 chips or 3 slots) after thePICH frame is transmitted. The protocol stack handler 910 maysynchronize with the paging cycle of the network, calculate the pagingoccasions of the PICH, and wake up at the right moment in time to listento its allocated PICH (e.g. by taking control of the radio resourcehardware over the protocol stack handler 920), and the protocol stackhandler 910 may wait and listen to the associated S-CCPCH (theassociated S-CCPCH arrives t_(PICH) after the PICH) for paging messagesif the PICH carries a PI message intended for the MS.

The protocol stack handler 910 may also be configured to perform powermeasurements of the neighbor cells with the first service network. Forexample, the protocol stack handler 910 may take control of the radioresource hardware to make the 2G power measurements 904 (e.g. RSSI ofBCCH and BSIC (Base Station Identity Code) for surrounding candidatecells). The 2G power measurements 904 made by the protocol stack handler910 may constantly interrupt the 3G PS data transfer 906, such that thedata rate associated with the second identity card may be damaged due tothe 2G power measurements 904 made for the first subscriber identitycard. Alternatively, in a UMTS/WCDMA network, the protocol stack handler910 makes power measurements to the CPICH (e.g. Ec/No, RSCP and so on)of candidate cells in a PM mode. When the first subscriber identity cardcorresponds to an LTE, LTE-A or WiMAX network, the protocol stackhandler 910 may make power measurements of different pilot signalsaccording to different RATs in the PM mode. The protocol stack handler910, when executed by the processor, performs power measurements ofcandidate cells and uses the power measurement results such as measuredsignal quality and/or signal strength of the BCCH, CPICH, or others asan input for handover and/or cell reselection decisions. From the powermeasurement results, the protocol stack handler 910 may make cellreselection decisions depending on different cell reselection criteriacorresponding to each radio access technology (RAT). For example, for aGSM network, the cell reselection criteria may be based on the C1 and C2criterions. For a UMTS network or a WCDMA network, there may be othercell reselection criteria such as a cell rank criteria or the Rcriteria.

In the embodiment in FIG. 8, when the protocol stack handler 910 isunable to find a suitable cell to camp on for the first subscriberidentity card, the protocol stack handler 910 may attempt to camp on acell irrespective of the PLMN identity, and enter a “limited service”state in which it can only attempt to make emergency calls. When theprotocol stack handler 910 is in a limited state and is not performing asearch procedure to recover from the limited service state, the purposeof the power measurements, the cell selection or cell re-selectionprocedures performed by the protocol stack handler 910 is only formaintaining the limited service state. However, the PS data rateassociated with the second identity card may still be damaged due to thepower measurements, the cell selection or cell re-selection proceduresmade by the first subscriber identity card. In this case, it is desiredto decrease the power measurements, the cell selection or cellre-selection procedures made by the protocol stack handler 910 in orderto enhance the PS data rate associated with the second identity card. Inanother embodiment, when the protocol stack handlers 910 is configuredto execute operations related to the first subscriber identity cardwhile the protocol stack handlers 920 is configured to executeoperations related to the second subscriber identity card, the firstsubscriber identity card supports 2 or more RATs, wherein the secondsubscriber identity card supports one of the RATs that is supported bythe first subscriber identity card. When the second subscriber identitycard performs a PS data service on-line, the paging monitoring, such asthe PI monitoring on the PICH and/or the paging message monitoring onthe PCH, and the inter-RAT power measurements associated with the firstsubscriber identity card may cause more damage to the PS data rateassociated with the second subscriber identity card. In this embodiment,it is desired to avoid the inter-RAT power measurements or handover to aRAT that causes less damage to the PS data rate associated with thesecond subscriber identity card.

FIG. 10 is a flow chart illustrating a method for enhancing the datarate for a packet-switched (PS) data service associated with the secondsubscriber identity card when the protocol stack handler 910 is in theidle mode for the first subscriber identity card by using the softwarearchitecture of FIG. 8 according to an embodiment of the invention. Theprotocol stack handlers 910 is configured to execute operations relatedto the first subscriber identity card while the protocol stack handlers920 is configured to execute operations related to the second subscriberidentity card. The first subscriber identity card may support one ormore RATs (e.g. a SIM card that supports a single GSM/GPRS RAT or a CSIMcard that supports both the CDMA RAT and the GSM/GPRS RAT), wherein thesecond subscriber identity card may support one of the RATs that issupported by the first subscriber identity card (e.g. the UMTS RAT, theCDMA RAT, or the GSM/GPRS RAT). Initially, the protocol stack handlers910 and 920 are in the idle mode, and the protocol stack handler 910enters a limited service state in which the protocol stack handler 910may only attempt to make emergency calls (Step S1002). The protocolstack handler 910 may enter the limited service state due to “Nosuitable cell” or other reasons. As described previously, if the MS isunable to obtain normal services from a PLMN, the MS may attempt to campon an acceptable cell, irrespective of its PLMN identity, so thatemergency calls can be made if necessary. Upon entering the limitedservice state, the protocol stack handler 910 may notify the protocolstack 920 when entering the limited service state (Step S1004). In thenotification for entering the limited service, the protocol stackhandler 910 may include information about the RAT being used. Theprotocol stack handler 920 may use a flag or marker to note thecondition when the protocol stack handler 910 enters a limited servicestate using the same RAT as the protocol stack handler 920, e.g. thedefault value of the flag or marker may be set to “OFF”, the value ofthe flag or marker may be set to “ON” when the protocol stack handler910 enters the limited service state using the same RAT as the protocolstack handler 920, and the value of the flag or marker may be set to“OFF” when the protocol stack handler 910 exits the limited servicestate. For example, the protocol stack handler 910 may notify theprotocol stack handler 920 upon entering the limited service state. Inthe notification for entering the limited service, the protocol stackhandler 910 may include the RAT being used (e.g. GSM/GPRS RAT). Theprotocol stack handler 920 may set the value of the flag or marker to“ON” when the protocol stack handler 920 is also using the GSM/GPRS RAT.

Subsequent to step S1004, the protocol stack handler 920 receives a userrequest from the application layer 930 to perform a PS data service suchas push e-mail, IM, or others, with an associated service network (e.g.the service network 120) using a certain RAT (e.g. the GSM/GPRS RAT)(Step S1006). In this embodiment, the protocol stack handlers 920 maycheck if the protocol stack handlers 910 uses the same RAT, and requestthe protocol stack handler 910 to switch to the same service networkwhen the same RAT is used. Next, the protocol stack handler 920 requeststhe protocol stack handler 910 to switch to the same service network(e.g. the service network 120) (step S1008). It is to be understood thatthe protocol stack handler 910 may still be in the limited service stateafter it switches to the same service network as instructed by theprotocol stack handler 920. In one embodiment, step S1008 may also beperformed after the protocol stack handler 920 starts the PS dataservice. For example, when the protocol stack handler 910 enters thelimited service state after the protocol stack handler 920 has alreadybegun with the PS data service session, the protocol stack handler 920may request the protocol stack handler 910 to switch to the same servicenetwork as soon as the protocol stack handler 920 receives the noticefor entering the limited service state of the same RAT from the protocolstack handler 910. Next, the protocol stack handler 910 switches to thesame service network (Step S1010).

After switching to the same service network, the protocol stack handler910 acknowledges to the protocol stack handler 920 that the same servicenetwork has been switched to (Step S1012). After the acknowledgementfrom the protocol stack handler 910 is received, the protocol stackhandler 920 starts to perform the PS data service instructed by theapplication layer 930 (Step S1014). In order to perform the PS dataservice, the protocol stack handler 920 may perform the GPRS attachprocedure as illustrated in FIG. 3 or the PDP context activationprocedure as illustrated in FIG. 4. Next, in Step S1016, the protocolstack handler 910 may reference the cell information obtained from theprotocol stack handler 920 for camping on the same cell. Taking GSM asexample, the cell information may include the frequency, the timing offrame 0 and/or the System Information broadcasted in BCCH. Taking UMTSas example, the cell information may include the system information, theneighbor cell list, the measurement results of the serving and neighborcells, and so on. It is noted that the protocol stack handler 910consumes less time to instruct the relevant RF module to performoperations camping on the same cell, which have to interrupt PS datatransfer for the second subscriber identity card, when obtaining moreinformation from the protocol stack handler 920. That is, more cellinformation sharing causes less damage to the PS data throughput for thesecond subscriber identity card. For example, when only obtaining thefrequency of the camp-on cell by the protocol stack handler 920, theprotocol stack handler 910 instructs the GSM/GPRS RF module to seektiming of the frame 0 at the obtained frequency, obtain SystemInformation from the BCCH, and so on. Contrarily, when obtaining allrequisite cell information from the protocol stack handler 920, theprotocol stack handler 910 has no need to perform any operation to campon the same cell as the protocol stack handler 920. Once the user makesan emergency call attempt with the first subscriber identity card, theprotocol stack handler 910, for example, can issue a random accesschannel (RACH) request to the same cell being camped on by the protocolstack handler 920 with reference to the collected cell information. Theprotocol stack handler 910 may obtain the cell re-selection informationfrom the protocol stack handler 920 to maintain mobility (Step S1018).Specifically, in one example, the protocol stack handler 920 mayactively notify the protocol stack handler 910 of new cell informationonce re-selecting to a new cell. In another example, the protocol stackhandler 910 may periodically ask the protocol stack handler 920 if acell-reselection occurs, for example, every 0.5 second, and if so,obtains new cell information therefrom. Similarly, as discussed above,more new cell information sharing causes less damage to the PS datathroughput for the second subscriber identity card.

While in the limited service state, the protocol stack handler 910 maystill perform the periodic PLMN search procedure to recover from thelimited service state, for example, every 20 seconds. As known by thoseskilled in the art, during the PLMN search procedure, the MS may performa power scan to find out proper cells to camp on. Once a successful PLMNsearch procedure is completed, the protocol stack handler 910 may findout proper cells to camp on and exit the limited service state (StepS1020). After exiting the limited service state, the protocol stackhandler 910 may notify the protocol stack handler 920 when exiting thelimited service state (Step S1022). Upon receiving the notification forexiting the limited service state, the protocol stack handler 920 mayset the value of the aforementioned flag or marker to “OFF” to indicatethat the protocol stack handler 910 has exited the limited servicestate. Upon exiting the limited service state, the protocol stackhandler 910 may also notify the application layer 930. The applicationlayer 930 may notify the user of the status related to the firstsubscriber identity card by showing messages such as “first subscriberidentity card in service” or others.

FIG. 11 is a message sequence chart illustrating the method forenhancing the data rate for a packet-switched (PS) data serviceassociated with the second subscriber identity card when the protocolstack handler 910 is in the idle mode for the first subscriber identitycard according to the embodiment of FIG. 10. The first subscriberidentity card may support one or more RATs (e.g. a SIM card thatsupports a single GSM/GPRS RAT or a CSIM card that supports both theCDMA RAT and the GSM/GPRS RAT), wherein the second subscriber identitycard may support one of the RATs that is also supported by the firstsubscriber identity card (e.g. the UMTS RAT, the CDMA RAT, or theGSM/GPRS RAT). Initially, the protocol stack handlers 910 and 920 are inthe idle mode, and the protocol stack handler 910 enters a limitedservice state in which the protocol stack handler 910 may only attemptto make emergency calls (Step S1102). The protocol stack handler 910 mayenter the limited service state due to “No suitable cell” or otherreasons. Upon entering the limited service state, the protocol stackhandler 910 may notify the protocol stack 920 when entering the limitedservice state (Step S1104). In the notification for entering the limitedservice, the protocol stack handler 910 may include information aboutthe RAT being used. The protocol stack handler 920 may use a flag ormarker to note the condition when the protocol stack handler 910 entersa limited service state using the same RAT as the protocol stack handler920. Subsequent to step S1104, the protocol stack handler 920 receives auser request from the application layer 930 to perform a PS data servicesuch as a push e-mail service request with the associated servicenetwork (e.g. the service network 120) using a certain RAT (e.g. theGSM/GPRS RAT) (Step S1106). Next, the protocol stack handler 920requests the protocol stack handler 910 to switch to the same servicenetwork (e.g. the service network 120) (step S1108). It is to beunderstood that the protocol stack handler 910 may still be in thelimited service state after it handover to the service network asinstructed by the protocol stack handler 920. Next, the protocol stackhandler 910 switches to the same service network and acknowledges to theprotocol stack handler 920 that the same service network has beenswitched to (Step S1110 and Step S1112). Reference for detaileddescriptions regarding the operations for switching of the servicenetwork may be made to the aforementioned descriptions relating to FIG.10. After the acknowledgement from the protocol stack handler 910 isreceived, the protocol stack handler 920 starts to perform the PS dataservice instructed by the application layer 930 (Step S1114). Next, theprotocol stack handler 910 may reference the cell information obtainedfrom the protocol stack handler 920 for camping on the same cell (Step1116). Taking GSM as example, the cell information may include thefrequency, the timing of frame 0 and/or the System Informationbroadcasted in BCCH. Taking UMTS as example, the cell information mayinclude the system information, the neighbor cell list, the measurementresults of serving and neighbor cells, and so on. It is noted that theprotocol stack handler 910 consumes less time to instruct the relevantRF module to perform operations camping on the same cell, which have tointerrupt PS data transfer for the second subscriber identity card, whenobtaining more information from the protocol stack handler 920. That is,more cell information sharing causes less damage to the PS datathroughput for the second subscriber identity card. For example, whenonly obtaining the frequency of the camp-on cell by the protocol stackhandler 920, the protocol stack handler 910 instructs the GSM/GPRS RFmodule to seek timing of the frame 0 at the obtained frequency, obtainSystem Information from the BCCH, and so on. Contrarily, when obtainingall requisite cell information from the protocol stack handler 920, theprotocol stack handler 910 has no need to perform any operation to campon the same cell as the protocol stack handler 920. Once the user makesan emergency call attempt with the first subscriber identity card, theprotocol stack handler 910, for example, can issue a random accesschannel (RACH) request to the same cell being camped on by the protocolstack handler 920 with reference to the collected cell information. Theprotocol stack handler 910 may obtain the cell re-selection informationfrom the protocol stack handler 920 to maintain mobility (Step S1118).

While in the limited service state, the protocol stack handler 910 maystill perform the periodic PLMN search procedure to recover from thelimited service state. Once a successful PLMN search procedure iscompleted, the protocol stack handler 910 may find out proper cells tocamp on and exit the limited service state (Step S1120). After exitingthe limited service state, the protocol stack handler 910 may notify theprotocol stack handler 920 when exiting the limited service state (StepS1122). Upon exiting the limited service state, the protocol stackhandler 910 may also notify the application layer 930. The applicationlayer may notify the user of the status related to the first subscriberidentity card by showing messages such as “first subscriber identitycard in service” or others.

FIG. 12A and FIG. 12B is a flow chart illustrating a method forenhancing the data rate for a packet-switched (PS) data serviceassociated with the second subscriber identity card when the protocolstack handler 910 is in the idle mode for the first subscriber identitycard by using the software architecture of FIG. 8 according to anotherembodiment of the invention. The protocol stack handler 910 isconfigured to execute operations related to the first subscriberidentity card while the protocol stack handler 920 is configured toexecute operations related to the second subscriber identity card.Specifically, the first subscriber identity card may support more thanone RAT (e.g. a CSIM card that supports both the CDMA RAT and theGSM/GPRS RAT). Initially, the protocol stack handlers 910 and 920 are inthe idle mode, and the protocol stack handler 920 receives a userrequest from the application layer 930 to perform a PS data service suchas push e-mail, IM, or others using a certain RAT (e.g. the CDMA RAT)(Step S1202). Next, the protocol stack handler 920 requests the protocolstack handler 910 to select a suitable target RAT before starting the PSdata service session (step S1204), wherein the target RAT is a RAT thatmay cause the least damage to the PS data rate of the PS data serviceassociated with the protocol stack handler 920. Specifically, theprotocol stack handler 910 may select a target RAT according to but notlimited to the following three target RAT factors:

(1) The Coverage of the Supported RATs:

Generally, a 2G network or 2G RAT has better coverage than a 3G networkor a 3G RAT in terms of radio frequency (RF) coverage. Therefore, whenthe protocol stack handler 910 listens to the PCH for paging messages,there is less chance for performing an out-of-service frequency scan.The protocol stack handler 910 selects the target RAT which has a betterRF coverage in order to avoid the out-of-service frequency scan.

(2) The Ability of the Physical Layer of the Supported RATs:

The ability of the physical layer of the supported RATs is the timeconsumption for the protocol stack handler 910 to perform operationsrelated to receive messages from the associated RAT and/or maintainmobility in the RAT. For example, the time consumed for performing theoperations to receive messages and/or maintain mobility, such as thefrequent power measurements and the monitoring of paging messages asdescribed in FIG. 9. The protocol stack handler 910 selects a suitableRAT which requires the minimum time to receive messages and/or maintainmobility.

(3) Whether it is Beneficial to Let the First and the Second SubscriberIdentity Cards Stay on the Same RAT:

When the first and the second subscriber identity cards stays in thesame RAT (e.g. GPRS), some improvements may be used to enhance the PSdata rate associated with the protocol stack handler 920. For example,the protocol stack handler 910 may reference the cell informationmeasured by the protocol stack handler 920, as described previously inFIG. 10 (Step S1206).

In one embodiment, the MS may have a pre-defined stored database of thesupported RAT coverage or the physical layer ability of the supportedRATs, wherein the supported RAT coverage database may include apredefined ranking in terms of the RF coverage for the supported RATs(e.g. the GSM RAT has a better RF coverage than the UMTS RAT), and thedatabase of the physical layer ability of the supported RATs may includea predefined list of the theoretical time to receive messages and/ormaintain mobility for the supported RATs. In another embodiment, the MSmay keep a dynamic record of the RF coverage and the physical layerability of the supported RATs. For example, the MS may keep a dynamicrecord of the call drop count due to a lack of RF coverage (or otherperformance metrics) for the supported RAT for a predefined duration(e.g. the most recent 24 hours). And the protocol stack handler 910 mayuse the dynamic record as a reference of the RF coverage in step S1206.In another embodiment, the protocol stack handler 910 may assigndifferent weighting ratios to the three suitable RAT factors whenselecting the suitable RAT. For example, the coverage of the supportedRAT may be assigned with 40% weighting ratio, the ability of thephysical layer of the supported RAT may be assigned with 35% ratio, andletting the first and the second subscriber identity cards stay on thesame RAT may be assigned with 25% weighting ratio. Alternatively, thecoverage of the supported RAT may be assigned with 30% weighting ratio,the ability of the physical layer of the supported RAT may be assignedwith 50% ratio, and letting the first and the second subscriber identitycards stay on the same RAT may be assigned with 20% weighting ratio. Itis to be understood that the protocol stack handler 910 may also performthe steps S1206 and S1208 to select and camp on a new target RAT whenthe protocol stack handler 910 loses coverage with the existing targetRAT. For example, when the existing target RAT no longer satisfies thereselection criteria (e.g. the C2 criterion in the GSM RAT and the Rcriterion in the UMTS RAT), the protocol stack handler 910 may go out ofservice if a cell selection procedure or a frequency scan is notperformed immediately to select another target RAT. In still anotherembodiment, the mentioned target RAT selection may be alternativelyperformed by the protocol stack handler 920, and notify the results(i.e. suggest target RAT) to the protocol stack handler 910.

After the target RAT has been selected in step S1206, the protocol stackhandler 910 further camps on the target RAT and disables the inter-RATmeasurement (Step S1208). That is, the protocol stack handler 910 campson one of the cells of the target RAT. After camping on the target RAT,the protocol stack handler 910 may perform normal circuit switched (CS)or PS operations with the target RAT. In step S1208, the protocol stackhandler 910 also disables the inter-RAT measurement, wherein theinter-RAT measurement is the power measurements made to a different RATsupported by the same subscriber identity card (e.g. the firstsubscriber identity card). It is to be understood that the inter-RATmeasurement may take a longer time than the intra-RAT measurement. Forexample, the required time to make GSM power measurements (e.g. the RSSIof BCCH) when the MS is using a GSM RAT (intra-RAT measurement) may beshorter than the required time to make GSM power measurements when theMS is using a CDMA RAT (inter-RAT measurement). In this case, performinginter-RAT measurement for the first subscriber identity card may causegreater damage to the PS data throughput of the second subscriberidentity card. As such, by selecting a suitable RAT in step S1206 anddisabling the inter-RAT measurement, the protocol stack handler 910 mayminimize the time required to receive messages or maintain mobilitywithin the associated service network.

Subsequent to step S1208, the protocol stack handler 910 acknowledges tothe protocol stack handler 920 that a suitable RAT has been selected andthe inter-RAT measurement has been disabled (Step S1210). The protocolstack handler 920 may use a flag or marker to note the condition whenthe protocol stack handler 910 has disabled the inter-RAT measurement,e.g. the default value of the flag or marker may be set to “OFF”, thevalue of the flag or marker may be set to “ON” when the protocol stackhandler 910 has disabled the inter-RAT measurement, and the value of theflag or marker may be set to “OFF” when the protocol stack handler 910has enabled the inter-RAT measurement. After the acknowledgement fromthe protocol stack handler 910 is received, the protocol stack handler920 may start to perform the PS data service instructed by theapplication layer 930 (Step S1212). In order to perform the PS dataservice, the protocol stack handler 920 may perform the GPRS attachprocedure as illustrated in FIG. 3 or the PDP context activationprocedure as illustrated in FIG. 4. At the same time, the protocol stackhandler 910 may receive messages (e.g. PI or paging messages) andperform measurements to maintain mobility (e.g. the RSSI of BCCH and/orthe RSCP and Ec/No of CPICH) with the selected target RAT (Step S1214).Next, the protocol stack handler 920 may detect that the PS data servicesession has been terminated (Step S1216). Specifically, the protocolstack handler 920 may detect a GPRS detach procedure performed or a PDPcontext deactivation procedure to end the current PS data servicesession. After the PS data service session has been terminated, theprotocol stack handler 920 may request the protocol stack handler 910 toenable the inter-RAT measurement (Step S1218). Upon receiving therequest from the protocol stack handler 920, the protocol stack handler910 may enable the inter-RAT measurement and perform the inter-RAT cellreselection according to the inter-RAT measurement results (Step S1220).Moreover, the protocol stack handler 920 may set the value of the flagor marker to “OFF” to indicate that the protocol stack handler 910 hasenabled the inter-RAT measurement.

FIG. 13 is a message sequence chart illustrating the method forenhancing the data rate for a packet-switched (PS) data serviceassociated with the second subscriber identity card when the protocolstack handler 910 is in the idle mode for the first subscriber identitycard according to the embodiment of FIG. 12A and FIG. 12B. Initially,the protocol stack handlers 910 and 920 are in the idle mode, and theprotocol stack handler 920 receives a user request from the applicationlayer 930 to perform a PS data service such as push e-mail (Step S1302).Next, the protocol stack handler 920 requests the protocol stack handler910 to select a suitable target RAT before starting the PS data servicesession (step S1304). The suitable RAT is a RAT that may cause the leastdamage to the PS data rate of the PS data service associated with theprotocol stack handler 920. Specifically, the protocol stack handler 910may select a suitable RAT according to but not limited to theaforementioned factors.

Reference for detailed descriptions regarding the methods for acquiringthe suitable RAT factors for the supported RATs may be made to theaforementioned descriptions relating to FIG. 12A and FIG. 12B. After atarget RAT has been selected in step S1306, the protocol stack handler910 camps on the target RAT and disables the inter-RAT measurement (StepS1308). Reference for detailed descriptions regarding the operations forcamping on the target RAT may be made to aforementioned descriptionsrelating to the operations for a PLMN search procedure. After camping onthe target RAT, the protocol stack handler 910 may perform normalcircuit switched (CS) or PS operations with the selected target RAT. Instep S1308, the protocol stack handler 910 also disables the inter-RATmeasurement.

Subsequent to step S1308, the protocol stack handler 910 acknowledges tothe protocol stack handler 920 that a suitable RAT has been selected andthe inter-RAT measurement has been disabled (Step S1310). After theacknowledgement from the protocol stack handler 910 is received, theprotocol stack handler 920 may start to perform the PS data serviceinstructed by the application layer 930 (Step S1312). At the same time,the protocol stack handler 910 may receive messages (e.g. PI or pagingmessages) and perform measurements to maintain mobility (e.g. the RSSIof BCCH and/or the RSCP and Ec/No of CPICH) with the selected target RAT(Step S1314). Next, the protocol stack handler 920 may detect that thePS data service session has been terminated (Step S1316). After the PSdata service session has been terminated, the protocol stack handler 920may request the protocol stack handler 910 to enable the inter-RATmeasurement (Step S1318). Upon receiving the request from the protocolstack handler 920, the protocol stack handler 910 may enable theinter-RAT measurement and perform the inter-RAT cell reselectionaccording to the inter-RAT measurement results (Step S1320).

FIG. 14 is a block diagram illustrating the software architecture of anMS according to another embodiment of the invention. Similar to FIG. 8,the exemplary software architecture also contains the protocol stackhandlers 910 and 920, and the application layer 930. Additionally, aresource reservation arbitrator (RRSVA) 940 is included, which solvesconflicts between the protocol stack handlers 910 and 920 and arbitrateswhich one of the protocol stack handlers 910 and 920 may occupy theradio resource hardware at a given time. The RRSVA 940 may beimplemented in program code and, when the program code is loaded andexecuted by the processing unit or MCU, granting or rejecting of radioresource requests issued by any of the protocol stack handlers 910 and920 in terms of predefined rules with the priorities of the requestedtraffics may be performed. The RRSVA 940 may also be implemented inprogram code to determine and switch the target service network or thetarget RAT for an idle subscriber identity card (e.g. the firstsubscriber identity card) in order to enhance the data rate of the PSdata traffic.

FIG. 15A and FIG. 15B is a flow chart illustrating a method forenhancing the data rate for a packet-switched (PS) data serviceassociated with the second subscriber identity card when the protocolstack handler 910 is in the idle mode by using the software architectureof FIG. 14 according to an embodiment of the invention. The protocolstack handlers 910 is configured to execute operations related to thefirst subscriber identity card while the protocol stack handlers 920 isconfigured to execute operations related to the second subscriberidentity card. The first subscriber identity card may support one ormore RATs (e.g. a SIM card that supports a single GSM/GPRS RAT or a CSIMcard that supports both the CDMA RAT and the GSM/GPRS RAT), wherein thesecond subscriber identity card may support one of the RATs that issupported by the first subscriber identity card (e.g. the UMTS RAT, theCDMA RAT, or the GSM/GPRS RAT). Initially, the protocol stack handlers910 and 920 are in the idle mode, and the protocol stack handler 910enters a limited service state in which the protocol stack handler 910may only attempt to make emergency calls (Step S1502). Upon entering thelimited service state, the protocol stack handler 910 may notify theRRSVA 940 for entering the limited service state (Step S1504). In thenotification for entering the limited service, the protocol stackhandler 910 may include information about the RAT being used. Next, theprotocol stack handler 920 receives a user request from the applicationlayer 930 to perform a PS data service such as push e-mail, IM, orothers, with an associated service network (e.g. service network 120)(Step S1506). After receiving the user request for performing the PSdata service, the protocol stack handler 920 requests the RRSVA 940 toperform the PS data service (Step S1508). In the request for performingthe PS data service, the protocol stack handler 920 may includeinformation about the RAT being used and the associated service network.Upon receiving the request from the protocol stack handler 920, theRRSVA 940 may request the protocol stack handler 910 to switch to thesame service network (e.g. the service network 120) (step S1510). Inthis embodiment, the RRSVA 940 may check if the protocol stack handlers910 and 920 use the same RAT, and request the protocol stack handler 910to switch to the same service network when the same RAT is used. Next,the protocol stack handler 910 switches to the same service network asthe protocol stack handler 920 (Step S1512). Reference for detaileddescriptions regarding the operations for switching to the same servicenetwork may be made to the aforementioned descriptions relating to FIG.10.

After switching to the same service network, the protocol stack handler910 acknowledges the RRSVA 940 that the same service network has beenswitched to (Step S1514). Upon receiving the acknowledgement, the RRSVA940 sends a grant for PS data service to the protocol stack handler 920(Step S1516). The protocol stack handler 920 starts to perform the PSdata service after receiving the grant (Step S1518). At the same time,the protocol stack handler 910 may reference the cell informationobtained from the protocol stack handler 920, and perform the operationsto maintain mobility (e.g. the cell selection/cell re-selection/LACupdate procedures) according to the cell information of the protocolstack handler 920 (Step S1520) for camping on the same cell. Taking GSMas example, the cell information may include the frequency, the timingof frame 0 and/or the System Information broadcasted in BCCH. TakingUMTS as example, the cell information may include the systeminformation, the neighbor cell list, the measurement results of servingand neighbor cells, and so on. It is noted that the protocol stackhandler 910 consumes less time to instruct the relevant RF module toperform operations camping on the same cell, which have to interrupt PSdata transfer for the second subscriber identity card, when obtainingmore information from the protocol stack handler 920. That is, more cellinformation sharing causes less damage to the PS data throughput for thesecond subscriber identity card. For example, when only obtaining thefrequency of the camp-on cell by the protocol stack handler 920, theprotocol stack handler 910 instructs the GSM/GPRS RF module to seektiming of the frame 0 at the obtained frequency, obtain SystemInformation from the BCCH, and so on. Contrarily, when obtaining allrequisite cell information from the protocol stack handler 920, theprotocol stack handler 910 has no need to perform any operation to campon the same cell as the protocol stack handler 920. Once the user makesan emergency call attempt with the first subscriber identity card, theprotocol stack handler 910, for example, can issue a random accesschannel (RACH) request to the same cell being camped on by the protocolstack handler 920 with reference to the collected cell information. Theprotocol stack handler 910 may obtain the cell re-selection informationfrom the protocol stack handler 920 to maintain mobility (Step S1522)

While in the limited service state, the protocol stack handler 910 maystill perform the periodic PLMN search procedure to recover from thelimited service state. Once a successful PLMN search procedure iscompleted, the protocol stack handler 910 may find out proper cells tocamp on and exit the limited service state (Step S1524). After exitingthe limited service state, the protocol stack handler 910 may notify theRRSVA 940 when exiting the limited service state (Step S1526). Uponreceiving the notification for exiting the limited service state, theRRSVA 940 may notify the application layer 930 that the protocol stackhandler 910 has exited the limited service state. Then, the applicationlayer may notify the user of the status related to the first subscriberidentity card by showing messages such as “first subscriber identitycard in service” or others.

FIG. 16A and FIG. 16B is a flow chart illustrating a method forenhancing the data rate for a packet-switched (PS) data serviceassociated with the second subscriber identity card when the protocolstack handler 910 is in the idle mode for the first subscriber identitycard by using the software architecture of FIG. 14 according to anotherembodiment of the invention. The protocol stack handlers 910 isconfigured to execute operations related to the first subscriberidentity card while the protocol stack handlers 920 is configured toexecute operations related to the second subscriber identity card.Specifically, the first subscriber identity card may support more thanone RAT (e.g. a CSIM card that supports both the CDMA RAT and theGSM/GPRS RAT). Initially, the protocol stack handlers 910 and 920 are inthe idle mode, and the protocol stack handler 920 receives a userrequest from the application layer 930 to perform a PS data service suchas push e-mail, IM, or others using a certain RAT (e.g. the CDMA RAT)(Step S1602). Next, the protocol stack handler 920 requests the RRSVA940 to perform the PS data service (step S1604). Upon receiving therequest, the RRSVA 940 sends a request to the protocol stack handler 910to select a suitable target RAT (Step S1606), wherein the target RAT isa RAT that may cause the least damage to the PS data rate to theprotocol stack handler 920. Specifically, the protocol stack handler 910may select a target RAT according to but not limited to theaforementioned factors.

Reference for detailed descriptions regarding the methods for acquiringthe suitable RAT factors for the supported RATs may be made to theaforementioned descriptions relating to FIG. 12A and FIG. 12B.

After the target RAT has been selected in step S1608, the protocol stackhandler 910 further camps on the target RAT and disables the inter-RATmeasurement (Step S1610). Reference for detailed descriptions regardingthe operations for camping on the target RAT may be made to theaforementioned descriptions. After camping on the target RAT, theprotocol stack handler 910 may perform normal circuit switched (CS) orPS operations with the target RAT. In step S1610, the protocol stackhandler 910 also disables the inter-RAT measurement, wherein theinter-RAT measurement is the power measurements made to a different RATsupported by the same subscriber identity card (e.g. the firstsubscriber identity card). By selecting a suitable RAT and disabling theinter-RAT measurement, the protocol stack handler 910 may minimize thetime required to receive messages or maintain mobility within theassociated service network.

Subsequent to step S1610, the protocol stack handler 910 acknowledges tothe RRSVA 940 that a suitable RAT has been selected and the inter-RATmeasurement has been disabled (Step S1612). Upon receiving theacknowledgement, the RRSVA 940 may send a grant for PS data service tothe protocol stack handler 920, After receiving the grant for PS dataservice, the protocol stack handler 920 may start to perform the PS dataservice instructed by the application layer 930 (Step 1616). At the sametime, the protocol stack handler 910 may receive messages (e.g. PI orpaging messages) and perform measurements to maintain mobility (e.g. theRSSI of BCCH and/or the RSCP and Ec/No of CPICH) with the target RAT(Step S1618). Next, the protocol stack handler 920 may detect that thePS data service session has been terminated (Step 1620). After the PSdata service session has been terminated, the protocol stack handler 920may notify the RRSVA 940 that the PS data service session has beenterminated (Step S1622). Upon receiving the notification, the RRSVA 940may request the protocol stack handler 910 to enable the inter-RATmeasurement (Step 1624). After receiving the request from the RRSVA 940,the protocol stack handler 910 may enable the inter-RAT measurement andreport to the RRSVA 940 that the inter-RAT measurement has been enabled(Step 1626). Then, the protocol stack handler 910 may perform theinter-RAT cell reselection according to the inter-RAT measurementresults.

While the invention has been described by way of example and in terms ofpreferred embodiment, it is to be understood that the invention is notlimited thereto. Those who are skilled in this technology can still makevarious alterations and modifications without departing from the scopeand spirit of this invention. For example, the software architectures ofFIGS. 8, 16, and 22 may each be implemented in program code stored in amachine-readable storage medium, such as a magnetic tape, semiconductor,magnetic disk, optical disc (e.g., CD-ROM, DVD-ROM, etc.), or others. AWeb server may store the software architectures of FIGS. 8, 16, and 22in a machine-readable storage medium, which can be downloaded by aclient computer through the Internet. When loaded and executed by theprocessing unit or MCU, the program code may perform the methods of FIG.12A, 12B, 14, 17, 19, 23 or 24, respectively corresponding to thesoftware architectures of FIGS. 8, 16, and 22. Although the embodimentsdescribed above employ the GSM/GPRS, WCDMA and/or UMTS basedtechnologies, the invention is not limited thereto. The embodiments mayalso be applied to other telecommunication network technologies, such asCDMA 2000, and TD-SCDMA, WiMAX, LTE, and TD-LTE technologies. Therefore,the scope of the present invention shall be defined and protected by thefollowing claims and their equivalents.

Use of ordinal terms such as “first”, “second”, “third”, etc., in theclaims to modify a claim element does not by itself connote anypriority, precedence, or order of one claim element over another or thetemporal order in which acts of a method are performed, but are usedmerely as labels to distinguish one claim element having a certain namefrom another element having a same name (but for use of the ordinalterm) to distinguish the claim elements.

1. A wireless communication device for enhancing a data rate for apacket-switched (PS) data service, comprising: a processor configured toreference cell information corresponding to a first subscriber identitycard to maintain mobility for a second subscriber identity card by usingthe referenced cell information when performing the PS data service witha first service network for the first subscriber identity card.
 2. Thewireless communication device of claim 1, wherein the processor furtherswitches the second subscriber identity card from a second servicenetwork to the first service network after a request is received toperform the PS data service with the first subscriber identity card. 3.The wireless communication device of claim 2, wherein the processorfurther determines whether the first subscriber identity card and thesecond subscriber identity card support a common radio access technology(RAT), and switches an association of the second subscriber identitycard from a second service network to the first service network when thefirst subscriber identity card and the second subscriber identity cardsupport the common RAT when the first subscriber identity card and thesecond subscriber identity card support the common RAT.
 4. The wirelesscommunication device of claim 1, wherein the second subscriber identitycard is in a limited service state.
 5. The wireless communication deviceof claim 4, wherein the processor further resumes scheduled measurementassociated with the second subscriber identity card after the secondsubscriber identity card exits the limited service state.
 6. Thewireless communication device of claim 5, wherein the second subscriberidentity card exits the limited service state after a correspondingPublic Land Mobile Network (PLMN) search procedure has been successfullycompleted.
 7. The wireless communication device of claim 4, wherein thecell information comprises a frequency, timing of a frame 0 or systeminformation broadcasted in a Broadcast Control Channel (BCCH), a servingcell, a neighbor cell list, measurement results of serving and neighborcells.
 8. The wireless communication device of claim 7, wherein theprocessor maintains the mobility for the second subscriber identity cardby using the referenced cell information comprises the steps of: seekingfor the timing of the frame 0 at the frequency of the BCCH; obtainingthe system information from the BCCH; camping on the serving cell of thefirst subscriber identity card after the timing of the frame 0 and thesystem information are acquired; and using the cell information of thefirst subscriber identity card to perform an emergency call attempt. 9.A wireless communication device for enhancing a data rate for apacket-switched (PS) data service, comprising: a processor configured todisable an inter-RAT (Radio Access Technology) measurement for a secondsubscriber identity card when performing the PS data service with afirst subscriber identity card.
 10. The wireless communication device ofclaim 9, wherein the processor further determines a target RAT to stayfor the second subscriber identity card according to an effect that thetarget RAT has on the data rate of the PS data service and directs thesecond subscriber identity card to camp on the target RAT.
 11. Thewireless communication device of claim 10, wherein the target RAT is aRAT that causes the least damage to the data rate of the PS dataservice.
 12. The wireless communication device of claim 10, wherein theprocessor re-determines the target RAT for the second subscriberidentity card when the target RAT no longer satisfies a reselectioncriterion.
 13. The wireless communication device of claim 9, wherein thesecond subscriber identity card supports more than one RAT.
 14. Thewireless communication device of claim 11, wherein the processordetermines and re-determines the target RAT for the second subscriberidentity card by considering one of the following: a coverage factor, aphysical layer ability factor, and a same RAT factor.
 15. The wirelesscommunication device of claim 10, wherein the processor directs thesecond subscriber identity card to camp on the target RAT by performingthe following steps: selecting a target cell of the target RAT; campingon the target cell of the target RAT for the second subscriber identitycard.
 16. A wireless communication method for enhancing a data rate fora packet-switched (PS) data service, comprising: referencing cellinformation corresponding to a first subscriber identity card; andmaintaining mobility for a second subscriber identity card by using thereferenced cell information when performing the PS service with thefirst subscriber identity card.
 17. The wireless communication method ofclaim 16, further comprising: switching the second subscriber identitycard from a second service network to the first service network afterreceiving a request to perform the PS data service with the firstsubscriber identity card;
 18. The wireless communication method of claim17, further comprising: determining whether the first subscriberidentity card and the second subscriber identity card support a commonradio access technology (RAT); and switching the second subscriberidentity card from a second service network to the first service networkwhen the first subscriber identity card and the second subscriberidentity card support the common RAT.
 19. The wireless communicationmethod of claim 16, wherein the second subscriber identity card is in alimited service state.
 20. The wireless communication method of claim19, further comprising: resuming the scheduled measurement associatedwith the second subscriber identity card after the second subscriberidentity card exits the limited service state.
 21. The wirelesscommunication method of claim 20, wherein the second subscriber identitycard exits the limited service state after a corresponding Public LandMobile Network (PLMN) search procedure has been successfully completed.22. The wireless communication method of claim 19, wherein the cellinformation comprises a frequency, timing of a frame 0 or systeminformation broadcasted in a Broadcast Control Channel (BCCH), a servingcell, a neighbor cell list, measurement results of serving and neighborcells).
 23. The wireless communication method of claim 22, whereinmaintaining the mobility for the second subscriber identity card byusing the referenced cell information comprises the steps of: seekingfor the timing of the frame 0 at the frequency of the BCCH; obtainingthe system information from the BCCH; camping on the serving cell of thefirst subscriber identity card directly after the timing of the frame 0and the system information are acquired; and using the cell informationof the first subscriber identity card to perform an emergency callattempt.
 24. A wireless communication method for enhancing a data ratefor a packet-switched (PS) data service, comprising: disabling aninter-RAT (Radio Access Technology) measurement of the second subscriberidentity card when performing the PS data service with a firstsubscriber identity card.
 25. The wireless communication method of claim24, further comprising: determining a target RAT to stay for the secondsubscriber identity card according to an effect that the target RAT hason the data rate of the PS data service and directs the secondsubscriber identity card to camp on the target RAT.
 26. The wirelesscommunication method of claim 25, wherein the target RAT is a RAT thatcauses the least damage to the data rate of the PS data service.
 27. Thewireless communication method of claim 25 further comprising:re-determining the target RAT for the second subscriber identity cardwhen the target RAT no longer satisfies a reselection criterion.
 28. Thewireless communication method of claim 24, wherein the second subscriberidentity card supports more than one RAT.
 29. The wireless communicationmethod of claim 28 further comprising: determining and re-determiningthe target RAT for the second subscriber identity card by consideringone of the following: a coverage factor, a physical layer abilityfactor, and a same RAT factor.
 30. The wireless communication method ofclaim 25, wherein directing the second subscriber identity card to campon the target RAT further comprises: selecting a target cell of thetarget RAT; camping on the target cell of the target RAT for the secondsubscriber identity card.